Combine water and ice cream topping in Large Micro-Cooker®; whisk until well blended using Stainless Whisk. Microwave, covered, on HIGH 5-6 minutes or until mixture comes to a full boil. Whisk until blended; stir in vanilla. (Mixture will be thin.) Carefully pour ice cream topping mixture over brownie batter in a circular pattern.

Bake, uncovered, 35-40 minutes or until sauce is bubbling around edges. (Top of brownie will appear very saucy, but will thicken as it cools.) Using Silicone Oven Mitt, carefully remove skillet from oven to Stackable Cooling Rack.